Yeah it's pretty easy to make text not show up in dark mode. Literally just set the text to black. Though, there's not really any reason somebody would manually change their text colour to black, since it's already set to black by default. Unless they were doing something weird on purpose.
But what if somebody wanted to make their text colour kinda purpley for some flourish, like this.
Actually... that's surprisingly almost readable on my computer monitor at least? Because that background is straight up #000000 black, which was probably on purpose to create as much contrast as possible for custom CSS.
It could actually be an issue when people want to create posts with things like this paper-like background though: customized light backgrounds without changing the default text colour. Could work the other way too, if people forget about light-mode. If you toggle on/off inverted colours you can see it's pretty bad. I think it's fine to have those edge cases though, and it comes down to user error if I'm not accounting for that feature.
games.
...! You sense something appear above.💡♥
☼
WOAH YOU FOUND ME!
Toss a 
chunk
to Eggbug.
Eggbug chews up the
chunk and most of it falls out of their mouth, onto the floor in scattered pieces.
"Haha! Okay your turn I'll count:
It definitely started as me wanting to just write my ideas while also demonstrating my ideas about the new feature. So, just the text disappearing and reappearing when you toggle "invert colours"